Process and apparatus for coating a controlled release product in a rotating drum

ABSTRACT

The present invention is directed to a process for coating a substrate in a rotating drum, wherein a pocket is created in a substrate bed into which pocket coating materials are delivered. Also provided is a controlled release product produced according to this process, and an apparatus for carrying out the process.

This application claims the benefit of U.S. Provisional Application No.60/631,409, filed Nov. 30, 2004.

This invention relates to an improved process and apparatus for coatinga substrate in a rotating drum.

BACKGROUND

Typically fertilizer granules are coated in a rotating drum by sprayingand/or dribbling coating components onto the top surface of the bed offertilizer granules. In this method, the coating materials, such ascastor oil and isocyanate, do not easily penetrate into the granule bed.One of the reasons for this is their high viscosity and surface tension,which inhibits penetration into the granule bed. Because these coatingmaterials do not readily penetrate into the bed, they first coat thedrum surface, and are subsequently transferred onto the surface of thefertilizer granules. In this two stage process, the coating materialscannot spread effectively on the surface of the fertilizer granuleswithin the time it takes for the castor oil and isocyanate to react toform polyurethane (approximately four minutes at 75° C.). A similarproblem exists when other coating materials, such as other thermoplasticpolymers or thermoset polymers, are used. Accordingly, cured or driedcoating material builds up on the drum surface. This coating build up onthe drum surface is called “fouling”.

In prior art processes, fouling is severe, especially on the drumsurface around the coating material nozzles. In many cases, the coatingdrum must be cleaned every two weeks. Not only is the cleaning processexpensive, but the production interruptions and higher raw materialconsumption negatively affects net profits. Moreover, fouling adverselyaffects the quality of the controlled release product.

Coating quality (and therefore product performance) is reduced in priorart processes since there is limited opportunity for coating materialsto mix in the stoichiometric ratios necessary to form the desiredoptimum coat on substrate granules. For instance, isocyanate istypically dribbled onto the surface of the granules in a narrow line,while castor oil is either dribbled or sprayed. In either case, theopportunity for mixing of these two components with each other and onthe surface of the granules is limited, even if the isocyanate andcastor oil are delivered substantially simultaneously. One reason forthis is that granules moving in a rotating drum exhibit a linear layerflow, with slow lateral mixing between layers.

Attempts have been made to improve the coating process in a rotatingdrum. One approach has been to dip injector nozzles into the fertilizerbed so coating components are injected into the fertilizer bedimmediately below the surface of the bed. (See, for example, U.S. Pat.No. 5,374,292; U.S. Pat. No. 5,547,486; U.S. Pat. No. 5,858,094; andU.S. Pat. No. 6,537,611.) However, there still remains a need in the artto further improve mixing and reduce fouling to increase the efficiencyof the coating process.

SUMMARY

In one broad aspect of the invention, there is provided a process forcoating a substrate in a rotating drum, wherein a pocket is created in asubstrate bed into which pocket coating materials are delivered.

The present invention is also directed to a controlled release productproduced according to the process of the invention.

In a further broad aspect, there is provided a rotatable drum forcoating a substrate comprising a mixing zone and a drying zone, whereinthe mixing zone comprises (a) one or more means for creating a pocket ina substrate bed, and (b) one or more means for delivering coatingmaterials into the drum.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates linear layer flow of substrate granules in a rotatingdrum.

FIG. 2 shows the simultaneous delivery of polymer coating, premix and/ormonomers into a hole or pocket in a granule bed created by a plow in arotating drum according to an embodiment of the invention.

FIG. 3 shows a number of possible shapes for a plow for use in a processof the invention.

FIG. 4 shows the simultaneous dribbling of polymer coating, premixand/or monomers along the back of a plow to multiple locations ontoand/or into a substrate granule bed according to an embodiment of theinvention.

FIG. 5 shows the use of the plow of FIG. 4 to simultaneously deliverypolymer coating, premix and/or monomers into a hole or pocket in agranule bed created by the plow.

FIG. 6 shows the use of burying devices to bury coating materials in ahole or pocket in a granule bed created by a plow according to anembodiment of the invention.

FIG. 7 shows the placement of a plow in the wet zone of a rotating drumand the effect on the dry zone when injection nozzles are placed infront of and behind the plow according to different embodiments of theinvention.

FIG. 8 shows a baffle structure and orientation in the dry zone of FIG.7 according to an embodiment of the present invention.

DETAILED DESCRIPTION

It has surprisingly been found that in a method for coating fertilizergranules in a rotating drum, there is significant reduction in foulingwhere a means is used to create a hole or pocket in the fertilizergranule bed, with the coating materials being delivered into the hole orpocket created. The means for creating the hole or pocket is notparticularly limited, and includes a mechanical device, such as a plow,or high pressure air. Where a mechanical device, such as a plow, is usedto create the hole or pocket in the fertilizer bed, it was furthersurprisingly found that substantially improved results are obtained whenthe coating materials are introduced behind the plow in the applicationsof coating materials to fertilizer.

The improved method of the invention not only reduces fouling, but thereis also improved mixing of the fertilizer granules with coatingmaterials. An improved controlled release profile is observed,suggesting that coating materials are more uniformly distributed ontothe granules because of improved mixing. Improved mixing also reducesthe time required to coat the fertilizer granules, resulting in shorterresidence drum times and improved efficiency.

Although preferred substrates are fertilizer and plant nutrients, theprocess of the invention could be applied to a variety of othersubstrates. Other examples of substrates include drugs, vitamins,etc.—any substrate for which controlled release delivery would bebeneficial, and which can be coated in a rotating drum.

If a fertilizer or plant nutrient material is coated, the fertilizer orplant nutrient material preferably comprises a water soluble compound.Preferably, the plant nutrient comprises a compound containing nitrogen,phosphorus, potassium, sulphur, micronutrients, or a mixture thereof. Apreferred plant nutrient comprises urea. Other examples of useful plantnutrients are ammonium sulphate, ammonium phosphate, diammoniumphosphate and mixtures thereof. Examples of useful micronutrientsinclude copper, zinc, boron, manganese, iron and mixtures thereof.Useful plant nutrient materials are also described in U.S. Pat. No.5,538,531 and U.S. Pat. No. 6,358,296.

A variety of coatings may be used on the substrate. Preferably, apolymer coating is used, and more preferably a thermoset polymer.Examples of thermoset polymers include those derived from phenolic,aminoplastic or epoxy resins, some polyesters, polysulphides, andpolyurethanes. The thermoset polymer is preferably derived from an epoxyresin. Yet more preferably, the thermoset polymer is a polyurethane or asubstituted polyurethane.

In a preferred embodiment, the thermoset polymer is formed by reacting apolyol or a mixture of polyols and an isocyanate or a mixture ofisocyanates. The polyol may be any hydroxy-terminated polyol, such as apolyether, polyester, polycarbonate, polydiene, polycaprolactone, or amixture thereof. Preferred are polyols such as hydroxy-terminatedpolyhydrocarbons, hydroxy-terminated polyformals, fatty acidtriglycerides, hydroxy-terminated polyesters, hydroxymethyl-terminatedpolyesters, hydroxymethyl-terminated perfluoromethylenes,polyalkylene-ether glycols, polyalkylene-arylene-ether glycols andpolyalkylene-ether triols. Preferred polyols include polyetheleneglycols, adipic acid-ethylene glycol polyesters, poly(butylene glycol),poly(propylene glycol) and hydroxy-terminated polybutadiene (see, forexample, British patent No. 1,482,213). More preferred are polyetherpolyols and most preferred are polyether polyols having a molecularweight in the range of from about 60 to about 20,000, more preferablyfrom about 60 to about 10,000 and most preferably from about 60 to about8,000.

Preferred polyols are also described in U.S. Pat. No. 5,538,531. In U.S.Pat. No. 5,538,531, polyols having from about 2 to about 6 hydroxygroups, and preferably having at least one C₁₀-C₂₂ aliphatic moiety, aredescribed.

Most preferably, the polyol is castor oil or a mixture of castor oilwith other polyols.

The polyol may also be derived from natural sources, such as soybean,corn, canola, and the like. Polyols derived from natural sources can beused as they are or can be used to derive a synthetic polyol, such as asynthetic polyol based on soybean oil, which is commercially availablefrom Urethane Soy Systems Corp. (Princeton, Ill.).

Another useful class of polyols are oleo polyols, such as described inU.S. Pat. No. 6,358,296.

A mixture of polyols may also be used, for instance, castor oil withethylene glycol, castor oil with oleo polyol, castor oil withpolyethylene glycol, castor oil with polypropylene glycol, or apolypropylene (or polyethylene) glycol mixture of different end groupsand molecular weight.

Any suitable isocyanate may also be used. Generally, the isocyanatecompound suitable for use may be represented by the general formula:Q(NCO)_(i)wherein i is an integer of two or more and Q is an organic radicalhaving a valence of i. Q may be a substituted or unsubstitutedhydrocarbon group (e.g., an alkylene or arylene group). Moreover Q maybe represented by the formula:Q¹-Z-Q¹wherein Q¹ is an alkylene or arylene group and Z is chosen from thegroup comprising —O—, —O-Q¹—, CO—, —S—, —S-Q¹-S— and —SO₂—. Examples ofisocyanate compounds which fall within the scope of this definitioninclude hexamethylene diisocyanate, 1,8-diisocyanato-p-naphthalene,xylyl diisocyanate, (OCNCH₂CH₂CH₂OCH₂O)2,1-methyl-2,4-diisocyanatocyclohexane, phenylene diisocyanates,tolylene diisocyanates, chlorophenylene diisocyanates,diphenylmethane-4,4′-diisocyanate, naphthalene-1,5-diisocyanate,triphenylmethane-4,4′4″-triisocyanate andisopropylbenzene-alpha-4-diisocyanate.

In another embodiment, Q may also represent a polyurethane radicalhaving a valence of i. In this case Q(NCO)_(i) is a compound which iscommonly referred to in the art as a prepolymer. Generally, a prepolymermay be prepared by reacting a stoichiometric excess of an isocyanatecompound (as described above) with an active hydrogen-containingcompound, preferably the polyols described above. In this embodiment,the polyisocyanate may be, for example, used in proportions of fromabout 30 percent to about 200 percent stoichiometric excess with respectto the proportion of hydroxyl in the polyol.

In another embodiment, the isocyanate compound suitable for use in theprocess of the present invention may be selected from dimers and trimersof isocyanates and diisocyanates, and from polymeric diisocyanateshaving the general formula:[Q″(NCO)_(i)]_(j)wherein both i and j are integers having a value of 2 or more, and Q″ isa polyfunctional organic radical. Such isocyanates may be used togetherwith compounds having the general formula:L(NCO)_(k)wherein k is an integer having a value of 1 or more and L is amonofunctional or polyfunctional atom or radical. Examples of isocyanatecompounds which fall within the scope of this definition includeethylphosphonic diisocyanate, phenylphosphonic diisocyanate, compoundswhich contain a ═Si—NCO group, isocyanate compounds derived fromsulphonamides (QSO₂NCO), cyanic acid and thiocyanic acid.

See also, for example, British patent No. 1,453,258 for other examplesof useful isocyanate compounds.

Non-limiting examples of suitable isocyanates include: 1,6-hexamethylenediisocyanate, 1,4-butylene diisocyanate, furfurylidene diisocyanate,2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,4′-diphenylmethanediisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenylpropanediisocyanate, 4,4′-diphenyl-3,3′-dimethyl methane diisocyanate,1,5-naphthalene diisocyanate, 1-methyl-2,4-diisocyanate-5-chlorobenzene,2,4-diisocyanato-s-triazine, 1-methyl-2,4-diisocyanato cyclohexane,p-phenylene diisocyanate, m-phenylene diisocyanate, 1,4-naphthalenediisocyanate, dianisidine diisocyanate, bitoluene diisocyanate,1,4-xylylene diisocyanate, 1,3-xylylene diisocyanate,bis-(4-isocyanatophenyl)methane,bis-(3-methyl-4-isocyanatophenyl)methane, polymethylene polyphenylpolisocyanates and mixtures thereof.

Particularly preferred isocyanates are those described in U.S. Pat. No.5,538,531 and U.S. Pat. No. 6,358,296.

An isocyanate mixture may be preferred for some coatings.

Preferably, the polyol and isocyanate are used in amounts such that theratio of NCO groups in the isocyanate to hydroxy groups in the polyol isin the range from about 0.5 to about 3.0, more preferably from about 0.8to about 2.0, and most preferably from about 0.9 to about 1.1.

In addition, a thermoset polymer may be formed by using aminegroup-terminated or mercaptan-terminated monomers. For instance aurea-formaldehyde resin may be used.

Additives may be included in the coating materials. For instance, if thecoating materials are hydrophilic, then they will be compatible withhydrophilic substrate surfaces and they will be easy to spread on thesurface. If the coating materials are hydrophobic however, there will bedifficulty in spreading the coating materials on the substrate surface.Under these circumstances, additives like wetting agents, flow agents,levelling agents and coupling agents may be used to improvespreadability. If the viscosity of the coating is high, an additive maybe also be used to improve spreadability.

Another function of additives is to increase the hydrophobicity of thecoating. Hydrophobic additives reduce the release rate of coatedsubstrate.

Preferred additives are organic additives, such as petroleum products,coal products, natural products and synthetic products. Lubricantsderived from these may also be used. Exemplary organic additives includecommercially available coating additives and paint additives (such aswetting agents, flow agents, levelling agents and coupling agents), wax,paraffin oil, bitumen, asphalt, oil derived from coal, canola oil,soybean oil, coconut oil, linseed oil, tung oil, vegetable wax, animalfat, animal wax, and forest products such as tall oil, modified talloil, tall oil pitch, and pine tar. Mixtures of these materials may alsobe used. Particularly preferred organic additives are hydrophobicmaterials.

If the organic additive is wax, preferred waxes are those described inU.S. Pat. No. 5,538,531 or a silicone wax, such as is available from DowCorning. Preferred waxes have a drop melting point of at least 10° C.,preferably between about 20° C. to about 120° C., and more preferablybetween about 30° C. to about 120° C. Most preferably, the wax issubstantially non-tacky below about 40° C. The preferred wax is a C₁₀+alpha-olefin, and more preferably a C₂₀₋₁₀₀ alpha-olefin. Mostpreferably, the wax is a C₃₀+ wax, such as is available commerciallyfrom Chevron Phillips Chemical Company.

The amount of organic additive may vary, depending on its purpose in themixture, as would be apparent to a person of skill in the art. Forinstance, for some commercially available additives, an amount as low as0.001% by weight of the coating composition may be used.

Preferred organic additives and amounts are those that improve therelease profile and mechanical handling of the polymer coated substrate.

In a drum, substrate granules exhibit a linear layer flow as shown inFIG. 1. The granules in contact with the drum wall and those proximateto the drum wall move in the direction of the drum due to frictionforces between the granules and (a) the drum wall and (b) otherproximate granules. However, due to these same friction forces betweengranules, the granules on the surface of the granule bed and distal tothe drum wall move in an opposite linear direction to the lineardirection of rotation of the drum. This effect results in a layered flowpattern, which inhibits penetration of coating components through thegranule bed. It was found that by creating a hole or pocket in thegranule bed, deeper penetration and a wider range of distribution ofcoating materials into the granule bed is achieved, and mixing isimproved. Also it changes the flow pattern of the granules—i.e. breaksup the linear flow pattern.

A variety of means can be used to create the hole or pocket in thegranule bed. Preferably the hole or pocket is created by a mechanicaldevice, such as a plow, or high pressure air. An example of a plow (10)creating a hole or pocket (20) in a substrate granule bed (30) in arotating drum (40) is shown in FIG. 2. Where a plow is used, a varietyof different shapes can be used, such as shown in FIG. 3. Preferably theplow has a linear arm, curved to create a scoop at the end (e.g., a bentangle iron), which will create the hole or pocket in the fertilizer bed.A sharply angled arm (e.g., a straight angle iron) is less preferred,although it too may be used.

In order to achieve a significant reduction in fouling, the plow mustdig into the granule bed. The approach angle of the plow with respect tothe substrate bed surface may be 5-175°, preferably 30-150°, morepreferably 40-140°, and more preferably still 45-145°. The optimumapproach angle of the plow with respect to the substrate granule bedsurface is related to the shape of the plow and can be determined by oneof ordinary skill in the art through routine experimentation.

The depth of the plow in the substrate bed may be 5-95% of the substratebed depth, preferably 10-90%, more preferably 20-80%, and morepreferably still 30-70%. The optimum depth is related to the plow shape,approach angle, and loading rate of the drum, and can be determined byone of ordinary skill in the art through routine experimentation.

The coating materials may be delivered substantially simultaneously, assingle or divided injections by spraying or dribbling, into the hole orpocket in the substrate granule bed. For instance, for a polyurethanecoated fertilizer, (a) premix (comprising a polyol and other coatingcomponents) or a polyol, and (b) isocyanate may be delivered into thehole or pocket through the same or different injection nozzles. FIGS. 4and 5 illustrate the delivery of polymer coating, premix and/or monomers(50, 60) in two injection streams behind the plow (10) into the hole orpocket (20) in the granule bed (30) of the rotating drum (40).

Where castor oil/premix comprising castor oil is used, the castor oil orpremix may be delivered into the hole or pocket by dribbling orspraying. Where isocyanate is used, the isocyanate is typically dribbledinto the hole or pocket, although it too may be sprayed. Surprisinglygood results have been obtained where the castor oil or premix and theisocyanate are dribbled, preferably substantially simultaneously behindthe plow.

For significant reduction in fouling, and improved mixing, the firstapplication of coating materials are delivered substantiallysimultaneously behind the plow. According to one theory for coatingfertilizer with polymer, when coating materials are delivered behind theplow, the materials begin mixing in the hole or pocket created such thatthe higher temperature premix or polyol helps to reduce the viscosityand surface tension of the isocyanate. This in turn increases thepenetration speed of the isocyanate into the granule bed. If the coatingmaterials are delivered in front of the plow, the materials are notdelivered directly into the hole or pocket and the opportunity formixing the reactive monomers is reduced. Improved mixing of the coatingmaterials allows for a more even coating to be produced. Improved mixingis particularly important for the first application of coatingmaterials.

The injection nozzles and pipes used to deliver coating materials may beinserted below the surface of the moving granule bed. Where theinjection nozzles are below the surface of the granule bed, there is agreater opportunity for mixing of coating components in the hole orpocket. Where the injection nozzles are inserted below the surface ofthe granule bed, the coating materials are typically dribbled into thehole or pocket.

Burying devices, such as shown in FIG. 6, can also be used to cover thehole or pocket (20) produced by a device such as a plow (10) or highpressure air. A preferred burying device is one or more blades (70). Bysealing the cut made by the plow or air with one or more buryingdevices, mixing may be further improved.

When the coating materials are delivered onto or into the granule bed,the materials wet the granules. This wetting of granules creates a “wetzone” (80) in the drum, which is illustrated in FIG. 7. The granulesstick together in this zone and move almost as a solid. In the wet zone,it is preferable for the granules to be subjected to a severe or rapidtumbling, mixing or rotating as described in co-pending U.S. patentapplication Ser. No. 10/868,646.

Coating components can also be delivered into the wet zone at multipledelivery points. If there is multiple delivery of coating components,multiple plows may also be used at each or some, but at least one, ofthese delivery points.

Once the coating begins to cure (e.g., thermoset polymer) or dry (e.g.,thermoplastic polymer), the coated granules enter the “dry zone”, inwhich the granules flow freely in a different flow pattern than whenwet.

During the curing or drying phase, coated particles come into contactresulting in granules caking together and defects (such as an unevencoating thickness, craters, tears, pinholes, etc.) forming on thecoating surface. To prevent these defects it is preferable to minimizecontact between coated particles in the dry zone. In order to do this,the average linear velocity of coated particles in the drum should bereduced. This may be done by reducing drum speed, decreasing drum size,introducing baffles, etc., and as described in co-pending U.S. patentapplication Ser. No. 10/868,646.

If the drum speed alone is reduced, it is preferably slowed to about 10%to about 80% of the speed of the drum in the wet zone. The same percentreduction also applies to the size of the drum, if it is the size thatis reduced.

Baffles can also be used to reduce the velocity of coated particles,depending on their orientation, height, and number. A preferred baffleorientation is shown in FIG. 8. Preferably the baffles are oriented in adifferent direction to the avalanche flow of the coated particles (i.e.,a direction different than or opposite to the rotational direction ofthe drum), resulting in a substantial reduction in velocity.

A combination of baffles and reduced drum speed/size can also be used.

It has been surprisingly observed, as illustrated in FIG. 7, that wherethe coating components in a first coating application are introducedbehind the plow in the wet zone, the length of the dry zone increases(90) over that where the components are introduced in front of the plow(100). This translates to a shorter mixing time, and a shorter overallcoating process.

A coating unit may be used in which multiple coating layers are appliedto substrate granules. For instance, a coating unit having multipleregions for sequential application of coating materials could be used,each region having a wet and dry zone. In the wet zone of the firstregion, a device to create a hole or pocket, such as a plow, is used. Ifa plow is used, preferably the coating nozzles and pipes are locatedbehind the plow. In the second and subsequent coating region wet zones adevice may also be used to make a hole or pocket, although it is lessimportant than in the first region wet zone. If a plow is used in thesecond and subsequent wet zones, it has been discovered that it is lessimportant for the coating nozzles and pipes to be located behind theplow in order for there to be a substantial reduction in fouling,although it is preferred to have the nozzles and pipes behind the plow.Preferably a coating unit is used which has three or four coatingregions.

The wet and dry zones may comprise the same physical region of thecoating drum. The distinction between “zones” in this embodiment issimply a way to describe the stage of the coating process betweenapplication of coating materials (wet zone) and stabilization ofcoating, i.e., curing or drying (dry zone).

In another embodiment, the wet and dry zones comprise two distinctphysical regions of the drum. For instance, the drum may be angled, suchthat substrate granules enter the drum at one end, comprising the wetzone, and move into the dry zone by gravitational force.

The wet and dry zones may also comprise two drums, connected in series.

Where there are multiple coating applications, a single drum may be usedor multiple drums may be used. Where multiple drums are used, a varietyof drum combinations can be used, including using one or more of thedrums or drum combinations described above.

Using a device such as a plow to create a hole or pocket in a granulebed in a first application of coating material to the granules,especially where coating materials are delivered behind the plow ifused, results in an improved controlled release product. It has beensurprisingly discovered that the product so produced exhibits animproved front-end (i.e., under ten days) water release rate incontrolled release profiling tests compared to product produced where(a) no plow is used, and (b) coating components are delivered in frontof the plow, if a plow is used.

The following examples are offered by way of illustration and not by wayof limitation.

EXAMPLE 1

A rotary coating unit was used, having three coating regions, with threegroups of nozzles and pipes, one group in each coating region.

In the wet zone of the first coating region, a premix (comprising castoroil) and isocyanate were simultaneously delivered through a pipe (i.e.,dribbling or spraying) behind a bent angle iron plow that was weldedinto the coating unit. In the second and third coating regions plowswere also used.

It was discovered that the plow helped to reduce the release rate of theproduct. It was also discovered that by introducing the premix andisocyanate behind the plow, the dry zone of the first coating regionincreased from about 1 to 1½ feet to approximately 5 feet. This increasein the dry zone is comparable to that of the second and third coatingregions, which was not achievable before adding a plow and deliveringcoating materials behind the plow. This indicates better spreading ofthe coating materials on the substrate.

By using this method, it was discovered that over a four day period inwhich the coating unit ran continuously, fouling thickness on the drumwall was reduced by about two-thirds.

Moreover, the controlled release urea (CRU) produced had a 15-20% Nrelease at day 7. This release rate is difficult to achieve both in theabsence of a plow and, if a plow is used, with the coating componentsadded in front of the plow in the first wet zone. The improved releaserate demonstrates an improved mixing in the first application of coatingto substrate.

The % N release of CRU produced according to the above process are shownin Table 1. TABLE 1 Day 7 Day 14 Day 21 (a) 42* 55 63 (b) 30 45 55 (c)20 28 38 (d) 15 22 30*% N release(a) No plow and spraying premix and dribbling isocyanate on the top ofthe substrate bed surface in the drum. (Control);(b) with plow and spraying premix and dribbling isocyanate in front ofthe plow;(c) with plow and spraying premix and dribbling isocyanate behind theplow; and(d) with plow and dribbling premix and isocyanate behind the plow.

The data shown in Table 1 indicate that delivering the coating materialsinto the pocket behind the plow can significantly reduce the nitrogenrelease rate over that of the Control (a)

The water release data for the controlled release fertilizer materialwas also determined in accordance with the following procedure.

Water Release Profile Test

A water release rate profile analysis was performed using a TechniconAutoAnalyzer™, calibrated and used pursuant to the teachings ofAutomated Determination of Urea and Ammoniacal Nitrogen (University ofMissouri, 1980).

The following procedure was used:

-   -   1. Accurately weigh 15 grams (±0.1 mg) of the sample into a        weigh dish. Record the weight of sample. Transfer the sample to        125 mL Erlenmeyer flask.    -   2. Add 75 mL of demineralized water and stopper the flask.    -   3. Gently swirl the sample and water until all the particles are        submersed.    -   4. Let the sample stand for a specified time at a constant        temperature (typically at room temperature).    -   5. Gently swirl the flask to mix the solution and decant only        the solution to a 100 mL volumetric flask.    -   6. Rinse the sample with demineralized water adding to the        volumetric flask.    -   7. Bulk to volume of volumetric flask and mix thoroughly.    -   8. If the test is to be repeated for another time period, repeat        starting at Step 2.    -   9. Once the Technicon AutoAnalyzer II is on line, transfer some        of this solution (or perform the required dilutions if        necessary) to the Technicon sample cups for analysis.    -   10. Record the results as parts per million N—NH₃ (read directly        from a Shimadzu Integrator).

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity ofunderstanding, it is readily apparent to those of ordinary skill in theart in light of the teachings of this invention that certain changes andmodifications may be made thereto without departing from the spirit orscope of the appended claims.

All publications, patents and patent applications cited in thisspecification are incorporated herein by reference as if each individualpublication, patent or patent application were specifically andindividually indicated to be incorporated by reference. The citation ofany publication, patent or patent application is for its disclosureprior to the filing date and should not be construed as an admissionthat the present invention is not entitled to antedate such publication,patent or patent application by virtue of prior invention.

It must be noted that as used in the specification and the appendedclaims, the singular forms of “a”, “and” “the” include plural referenceunless the context clearly indicates otherwise.

Unless defined otherwise all technical and scientific terms used hereinhave the same meaning as commonly understood to one of ordinary skilland the art to which this invention belongs.

1. A process for coating a substrate in a rotating drum, wherein apocket is created in a substrate bed into which pocket coating materialsare delivered.
 2. The process according to claim 1, wherein thesubstrate is fertilizer granules.
 3. The process according to claim 1,wherein the pocket is created by a mechanical device or high pressureair.
 4. The process according to claim 1, wherein the pocket is createdby a plow means.
 5. The process according to claim 4, wherein thecoating materials are delivered behind the plow means.
 6. The processaccording to claim 1, wherein the coating materials are delivered on thesurface of the granule bed.
 7. The process according to claim 1, whereinthe coating materials are delivered below the surface of the granulebed.
 8. The process according to claim 1, wherein the coating materialsare substantially simultaneously delivered onto the surface of thesubstrate bed by spraying or dribbling.
 9. The process according toclaim 1, wherein a device is used to bury the coating materials in thepocket.
 10. The process according to claim 9, wherein the burying deviceis one or more blades.
 11. The process according to claim 1, wherein thedrum comprises one or more baffles.
 12. The process according to claim11, in which the baffles are oriented in a direction opposite to thedrum's direction of rotation.
 13. A controlled release product producedaccording to the process of claim
 1. 14. A rotatable drum for coating asubstrate comprising a mixing zone and a drying zone, wherein the mixingzone comprises (a) one or more means for creating a pocket in asubstrate bed, and (b) one or more means for delivering coatingmaterials into the drum.
 15. The drum of claim 14, wherein the means forcreating the pocket is a plow or high pressure air.
 16. The drum ofclaim 14, wherein the means for delivering the coating materials is anozzle or pipe, or a combination thereof.
 17. The drum of claim 14,wherein means for creating the pocket is a plow, and the means fordelivering coating materials into the drum are located behind the plow.18. The drum of claim 14, further comprising baffles, oriented in adirection opposite the direction of rotation of the drum.